• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.264-266
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• 2004

본 연구에서는 4차 암모늄염의 대전방지 현상을 알아보기 위하여 아크릴기가 있는 2-(dimethyl amino)ethyl methacrylate(DMA)를 알킬화 시켜 대전방지제를 합성하고, 자외선 경화 반응을 통해 대전방지 기능이 지속적으로 유지되게 하였다. 여기에서 얻어진 대전방지제를 PMMA 판에 코팅하여 코팅 도막의 전기저항의 변화를 관찰한 결과, 대전방지제의 함량이 20part 이상으로 높아질 때 표면저항 값이 낮아지는 현상을 볼 수 있었다. 또한 대전방지제의 함량이 10part인 경우, 상대습도가 $20\%$ 증가할 때 저항 값은 $10^2{\Omega}/cm^2$까지 감소하는 결과를 볼 수 있었다.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.387-392
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• 1996

Natural zeolite/epoxy resin composites were prepared and the cure kinetics was studied by dynamic DSC analysis. With the increments of natural zeolite content, the reaction starting temperature and the exothermic peak temperature were decreased. When diglycidyl ether of bisphenol A(DGEBA)/4,4'-methylene dianiline(MDA)/malononitrile(MN, 10phr) was filled with 20phr of zeolite, DSC thermogram had one peak and when it was filled with 30phr of zeolite, a shoulder appeared on the DSC thermogram. With the filling of 40phr of zeolite, DSC thermogram was separated into two peaks and the activation energy of the first peak, $Ea_1$ was 12.30 kJ/mol and that of the second peak, $Ea_2$ was 12.70 kJ/mol.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.581-586
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• 2005

High-performance concrete (HPC), which is particularly sensitive to self-desiccation, is required to be durable even in severe environmental conditions, i.e. costal area, cold district, etc. However, in recent years, some attention was particularly given to cracking sensitivity of high performance concrete at early age. It has been argued and demonstrated experimentally that such concrete undergoes autogenous shrinkage due to self-desiccation at early age under restrained condition, nd, as a result, internal tensile stress may develop, leading to micro cracking and macro cracking. This shrinkage-introduced crack produces a major serviceability problem for concrete structures. One possible method to reduce cracking due to autogenous shrinkage is the addition of expansive additive. Tests conducted by many researches have shown the beneficial effects of addition of expansive additive for reducing the risk of autogenous shrinkage-introduced cracking. However, the research on hydration model of expansion additive has been hardly researched up to now. This paper presents a study of the hydration model of Ettringite-Gypsum type expansive additive. As a result of comparing forecast values with experiment value, proposed model is shown to expressible of hydration of expansive additive.

• Journal of the Korea Society of Computer and Information
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• v.25 no.10
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• pp.115-123
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• 2020

In this paper, we propose to evaluate the potential anti-inflammatory properties of root bark extract of Cudrania (C.) tricuspidata on lipopolysaccharide (LPS)-induced inflammation in macrophages of apolipoprotein E (ApoE) knockout (ApoE^-/-) mice, murine model of atherosclerosis. Atherosclerosis is a chronic vascular inflammatory disease. C. tricuspidata is a small tree of the Moraceae family and its extract has anti-inflammatory activities. However, its role in the progress of atherosclerosis is not yet clear. To determine anti-inflammatory effects of C. tricuspidata in atherogenesis, we applied LPS in peritoneal macrophages of ApoE^-/- mice and measured cell viability by CCK-8 and expression of pro-inflammatory cytokines by qRT-PCR following treatment with root bark extract of C. tricuspidata. Research data was expressed as differences between the cells treated with LPS and root bark extract and the cells treated with LPS alone (control) by a two-tailed non-parametric Mann-Whitney U-test using GraphPad Instat program. No cytotoxic effect was observed when the cells were treated with the extract at concentrations ≤ 100 ㎍/mL. The expression of inflammatory cytokines, including MCP-1, IL-1β, IFN-γ, TNF-α, and IL-6 were inhibited by the extract. These results indicated that the extract has an anti-inflammatory effect and therefore a possible role in the treatment of atherosclerosis.

• Journal of the Korean Chemical Society
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• v.47 no.5
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• pp.472-478
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• 2003

In this work, the zeolite/diglycidylether of bisphenol A(DGEBA) systems were investigated in terms of the cure kinetics and mechanical interfacial properties of the composites. The 4, 4-diamino diphenyl methane(DDM) was used as a curing agent for epoxy. Two types of zeolite(PZ) were prepared with 15 and 35 wt% KOH treatments(15-BZ and 35-BZ, respectively) for 24 h, and their surface characteristics were studied by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction(XRD). Cure kinetics of the composites were examined in the context of differential scanning calorimetry(DSC), and mechanical interfacial properties were investigated in critical stress intensity factor($K_{IC}$) and critical strain energy release rate($G_{IC}$). In the results of XPS and XRD, sodium ion(Na) of zeolite was exchanged for potassium ion(K), resulting from the treatment of KOH. Also, $Si_{2p}/Al{2p}$ composition ratios of the treated zeolite were increased, which could be attributed to the weakening of Al-O bond in framework. Cure activation energy($E_a$) of 15-BZ composites was decreased, whereas KIC and $G_{IC}$ were increased, compared with those of the pure zeolite/DGEBA composites. It was probably accounted that the acidity of zeolite was increased by surface treatments and the cure reaction between zeolite and epoxy was influenced on the increased acidity of zeolite.

• Applied Chemistry for Engineering
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• v.24 no.2
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• pp.148-154
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• 2013

UV curable acryl resin, pressure-sensitive adhesives (PSAs), are used in many different parts in the world. In particular, PSAs has been used in the wafer manufacturing process of semiconductor industry. As wafers become much thinner, UV curable PSAs require more proper adhesion performance. In this study, acrylic PSAs containing hydroxyl groups were synthesized using monomers of 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene monomer and 2-hydroxyethyl acrylate. Isocyanate modified UV curable PSAs were then prepared by the adduct reaction that facilitates the UV curing property via controlling the amount of methacryloyloxyehtyl isocyanate. The proper adhesion performance and UV curing behavior of UV curable PSAs with various hydroxyl values were studied, and experimental conditions were then optimized to raise the efficiency of wafer manufacturing process. It was found that in case of using the equivalent ratio of 1 : 1 isocyanate hardener used in the UV curable PSAs, the peel strength before the UV curing process decreased as the amount of hydroxyl groups increased in the PSAs. The peeling adhesive strength was also decreased with increasing UV dose due to high curing characteristics.

• Childhood Kidney Diseases
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• v.13 no.2
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• pp.170-175
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• 2009

Purpose : FSGS do not respond well to any kind of therapy and gradually progress to end-stage renal disease. This study was conducted to investigate the difference of protein expression between MCNS and FSGS as a preliminary study for understanding the pathophysiology of FSGS. Methods : Renal biopsy samples of MCNS and FSGS were obtained, which was diagnosed by one pathologist. They were solubilized with a conventional extraction buffer for protein extraction. The solution was applied on immobilized linear gradient strip gel (pH 4-7) using IPGphor system. Silver staining was carried out according to standard method. Protein identification was done by searching NCBI database using MASCOT Peptide Mass Fingerprint software. Results : The differences in protein expressions between MCNS and FSGS were shown by increased or decreased protein spots. Most prominently expressed spot among several spots in FSGS was isolated and analyzed, one of which was glutathione S-transferase (GST) P1-1, whereas it was not found in MCNS. So GSTP1-1 was considered as the one of the key biomarkers in pathogenesis of FSGS. Conclusion : This result would be helpful in diagnosing FSGS and researching FSGS. Further studies for glutathione S-transferase P1-1 might be necessary to elucidate the mechanisms regarding FSGS.

• Polymer(Korea)
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• v.25 no.3
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• pp.359-366
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• 2001

Isothermal physical aging of a glass fiber/epoxy composite was examined at different aging temperatures ($T_a$) and degrees of conversion (monitored by the glass transition temperature, $T_g$) by means of the TBA torsion pendulum technique. The range of aging temperature was from 10 to $130^{\circ}C$ : the conversion was systematically changed from $T_g$=$76^{\circ}C$ to $T_g$=$177^{\circ}C$ (fully crosslinked). The effect of isothermal physical aging was manifested as perturbations of the modulus and mechanical loss vs. temperature in the vicinity of $T_a$ for all conversions. The rate of isothermal physical aging determined from the change of modulus with aging time at fixed aging temperature decreased and then increased with increasing conversion below T$_{a}$=9$0^{\circ}C$. There exists a superposition in aging rate vs. ($T_g$ -$T_a$) by shifting horizontally and vertically. This implies that the physical aging process is independent of the change of chemical structure as conversion proceeds. It has been found that water absorbed at the aging temperature below $70^{\circ}C$ during isothermal physical aging lowers the apparent aging rate. It is due to the absorbed water molecules forming strong polar interactions with hydroxyl group on network chain and reducing the segmental mobility during the physical aging.g.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.443-450
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• 2021

The effects of blast furnace slag(BFS) and desulfurized gypsum(FDG) on the compressive strength of CFBA, and self-hydration of CFBA were studied. CFBA has self-hydrating and hardening properties, and it can be seen that the compressive strength of CFBA can be improved by using appropriate amounts of BFS and FDG. In addition, the self-hardening properties of CFBA are similar to the hydration reaction of 4CaO·Al₂O₃·Fe₂O₃ (C₄AF), a cement clinker mineral, and when free-CaO, CaSO₄ and CaCO₃ coexist, Compressive strength of CFBA is expressed by the formation of calcium carbo compounds and hydrates of ettringite, calcium silicate, and calcium aluminate.

• Journal of the Korean Chemical Society
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• v.41 no.6
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• pp.299-303
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• 1997

The rate constants($k_{OH}$) for the alkaline hydrolysis of the 4-substituted phenyl ethyl benzylphosphonates were determined in various buffer solutions by UV(Vis spectrophotometer. The activation entropies of the title reactions show negative values and this result is not consistent with a dissociative mechanism (EA) for which a positive or slightly negative value of the entropy of activation should be expected. An associative mechanism(AE) is favorable because the negligible negative charge is generated on the leaving group in the rate determining step from a good Hammett relationship(ρ=1.89). By the results of a kinetic study, we conclude that a dissociative mechanism is not proceeded in the title reactions.